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Supernova Secrets Seen In X-Rays

samzenpus posted about 2 months ago | from the check-it-out dept.

Space 23

wjcofkc writes "CNN reports that astronomers using NASA's NuSTAR telescope have for the first time mapped deep within the radioactive material from a supernova. The light from the originating star, Cassiopeia A, located about 11,000 light-years away and having had about eight time the mass of our sun, first reached Earth about 350 years ago. But that does not mean there still isn't a lot to study. Scientists using the NuSTAR, which stands for Nuclear Spectroscopic Telescope Array, launched in June 2012 and consisting of an instrument with two telescopes that focus high energy X-ray light, were able to peer deep within the cataclysmic aftermath. While there is currently no model for how the process of a supernova works, the findings in the study are a big step forward. 'Until we had NuSTAR, we couldn't see down to the core of the explosion,' Brian Grefenstette, lead author and research scientist at the California Institute of Technology, said at a news conference Wednesday."

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23 comments

Wilhelm Roentgen Would be Proud (2)

Publiu5 (3542707) | about 2 months ago | (#46292803)

The marvels of x-ray radiation: not only can they shed light in the inner workings of humans, but also the stars themselves...

Re:Wilhelm Roentgen Would be Proud (4, Informative)

daknapp (156051) | about 2 months ago | (#46293041)

Unfortunately, in this case the observed photons were actually low-energy gamma rays. I guess they are called "x-rays" in the article because they fall into the region of the electromagnetic spectrum that is usually associated with x-rays. Ti-44 undergoes electron capture to Sc-44, which emits the two gamma rays at 78 and 68 keV, and then the Sc-44 decays (again by electron capture) to Ca-44.

But they are not true x-rays.

Re:Wilhelm Roentgen Would be Proud (1)

wonkey_monkey (2592601) | about 2 months ago | (#46293113)

There is no universal consensus for a definition distinguishing between X-rays and gamma rays.

Re:Wilhelm Roentgen Would be Proud (4, Interesting)

daknapp (156051) | about 2 months ago | (#46293149)

Universal, no, but physicists agree, and, really, who else matters? X-rays are emitted by electrons (atomic transitions or bremsstrahlung); gamma rays by nuclear transitions. Those definitions have been pretty well agreed upon by physicists for at least the last 15 years.

Astronomers, however, seem to characterize photons only by energy, which kind of makes sense if you realize that they frequently don't know the origin of the observed photons and build instruments for energy ranges instead.

But nonetheless it is still incorrect to characterize these photons as "x-rays."

Re:Wilhelm Roentgen Would be Proud (5, Informative)

Anonymous Coward | about 2 months ago | (#46293323)

No it is not incorrect. Your definition comes from nuclear physics but X-rays and gamma rays can and are produced in other ways too. Electrons can just as well emit gamma rays, for example in inverse Compton scattering processes. And gamma rays are produced in inelastic proton scatterings. As you say, in astrophysics we classify based on energy and typically keV photons are X-rays and MeV photons and up are gamma rays.

Re:Wilhelm Roentgen Would be Proud (1)

Anonymous Coward | about 2 months ago | (#46294091)

Electrons can just as well emit gamma rays, for example in inverse Compton scattering processes. And gamma rays are produced in inelastic proton scatterings.

In some sense, the GP was correct because in some subfields, the photons emitted by those processes would be labeled as x-rays. Where the GP failed was not for the distinction between x-rays and gamma rays by source process, but for insisting that those subfields are the only valid definition. For better or worse, there are several technical definitions/jargon words that change definition with field, although in this case it is a lot less confusion compared to say the definition of a metal being any element other than hydrogen or helium.

Re:Wilhelm Roentgen Would be Proud (0)

Anonymous Coward | about 2 months ago | (#46294111)

I agree. This is what wonkey_monkey and I (I am the AC above) tried to convey.

Wiki defn. (1)

justthinkit (954982) | about 2 months ago | (#46294349)

Wiki: [wikipedia.org]

The distinction between X-rays and gamma rays has changed in recent decades. Originally, the electromagnetic radiation emitted by X-ray tubes almost invariably had a longer wavelength than the radiation (gamma rays) emitted by radioactive nuclei. Older literature distinguished between X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10â'11 m, defined as gamma rays. However, with artificial sources now able to duplicate any electromagnetic radiation that originates in the nucleus, as well as far higher energies, the wavelengths characteristic of radioactive gamma ray sources vs. other types, now completely overlap. Thus, gamma rays are now usually distinguished by their origin: X-rays are emitted by definition by electrons outside the nucleus, while gamma rays are emitted by the nucleus.

Re:Wiki defn. (0)

Anonymous Coward | about 2 months ago | (#46294653)

That definitions is very flawd as I described above. Free electrons can and do produce gamma rays. Most of the VHE gamma rays detected by Cherenkov telescopes like VERITAS and HESS come from electrons. High energy inelastic proton scattering also produce gamma rays and those are not due to nuclear transitions. So again, that is how nuclear physicists define it. But it is not the ONLY definition which is what wonkey_monkey pointed out.

Re:Wilhelm Roentgen Would be Proud (0)

Anonymous Coward | about 2 months ago | (#46347051)

And on Slashdot we measure vitriol in X-Bones and Betas

Re:Wilhelm Roentgen Would be Proud (1)

marcosdumay (620877) | about 2 months ago | (#46294661)

But nonetheless it is still incorrect to characterize these photons as "x-rays."

Looks like for astronomers, the correct name is "x-rays". At least, you said so. And that being an article about astronomy...

No model? (0)

Anonymous Coward | about 2 months ago | (#46292815)

While there is currently no model for how the process of a supernova works

Does anybody actually believe that?

Re:No model? (2)

Urkki (668283) | about 2 months ago | (#46293013)

I Think it means, no working model, which would match observations. In current models supernovas do not happen reliably, the stars fail to actually go supernova. Is it a supernova model, if there's no supernova happening according to the model?

Re:No model? (2)

jaharris87 (1599603) | about 2 months ago | (#46299639)

State-of-the-art models produce reliable explosions in 2D with a neutrino heating mechanism, but given the extraordinary computational cost of three-dimensional simulations (one model costs ~100 million hours of total compute time), the jury is still out on if these models will explode with no imposed spatial symmetry. Despite this, it's looking more and more like we understand the fundamental principles of the mechanism, and a lack of a supernova in one of these 3D supernova models is more likely to be the result of an unjustified approximation or technical oversight in the numerical analysis.

Considering xtians don't believe in xrays... (-1)

Anonymous Coward | about 2 months ago | (#46292859)

I'm surprised more people don't laugh at the irony. I'm curious how they're going to explain this one away.

No model eh? (2, Informative)

Anonymous Coward | about 2 months ago | (#46292865)

http://en.wikipedia.org/wiki/Supernova#Current_models
http://arxiv.org/find/all/1/all:+AND+modelling+supernova/0/1/0/all/0/1

Slashdot editing at it's finest.

No comments in 1 hour (0, Offtopic)

Anonymous Coward | about 2 months ago | (#46292961)

Every1 must be over at Soylent chatting it up. Which seems fitting since Alice Hill and her Dice MBA minions / overlords are simply here to butcher this community and make this site nothing but a soulless traffic whoring Slashington Post.

Slashdotters, your new home where you are treated liked a community and not an "audience". Your voice is respected over there. All welcome. You don't have to suck down the bitter Beta pill here if you don't want to.

http://soylentnews.org/ [soylentnews.org]

Captcha fitting - Protest.

Re:No comments in 1 hour (1)

Sepodati (746220) | about 2 months ago | (#46293841)

First comment was 8 minutes after the summary was posted.

Why are you still here? You know what's more annoying than beta? The kid that has to come around every day to tell you that he's leaving. This time for good. I mean it. I really do. I'm being serious here, guys. I'm out. I'm leaving.

Re:No comments in 1 hour (0)

Anonymous Coward | about 2 months ago | (#46297689)

Indeed. Also notice that he posted at two in the morning my time, not many people on this side of the globe awake then. There's no more reasom to bitch about beta, there is an alternative. And I wish folks would stop pimping them here, because the thing that's worse than beta is all the non-nerds who have overrun this place lately. So far they haven't found the alternative (a good thing).

slashdot -- news for nerd wannabes. Sad.

How are xrays focused? (0)

Anonymous Coward | about 2 months ago | (#46296313)

How does this telescope focus x-rays? I thought there existed no such thing as an x-ray lens, which is why x-ray crystallography is computationally difficult.

TI ??? (0)

Anonymous Coward | about 2 months ago | (#46297781)

In my misspent youth ( I date myself) I had a TI52 and a TI58, strangely, nether of these ever showed any signs of decay, although the 52 did vanish one day...

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